Microfluidic Study on the Effect of Single Pore–Throat Geometry on Spontaneous Imbibition

Spontaneous imbibition is a naturally occurring phenomenon in porous media that plays an important role in various processes. Particularly during the oil recovery process, imbibition efficiency could be significantly affected by the physical properties of the reservoir rock, such as pore-throat structure. However, the effect of the pore-throat structure on the imbibition process has rarely been investigated quantitatively. Therefore, in this study, spontaneous imbibition was examined quantitatively using microfluidic devices with different single pore-throat geometries. Three key geometric parameters were examined, namely, pore-throat ratio, coordination number, and tortuosity. The pore-to-throat ratio of a single pore-to-throat structure under investigation ranges from 3 to 50. Designated coordination numbers range from 2 to 6. Tortuosity values for meandering channels range from 1 to 2. Imbibition process was mimicked using microfluidic devices with varying pore-throat geometries. The results showed that average imbibition velocity exhibited an initial increase followed by a subsequent decline with the increase in the pore-throat ratio. As the coordination number increased, imbibition velocity decreased as the coordination number increased, and the influence of the pore-throat ratio diminished as the coordination number increased. Imbibition velocity decreased as the tortuosity increased. Meniscus movements were investigated for different pore-throat structures. Statistical analysis was also conducted to determine the dominant factor governing the imbibition behavior. It was found that pore-throat ratio, tortuosity, and coordination number exerted a decreasing impact on the imbibition velocity. Wetting phase saturation was examined over time using a single pore-throat geometry device with varying pore-throat ratios. Four distinct types of imbibition behaviors were identified and characterized. In conclusion, this work examined the imbibition behaviors within specified pore-throat geometries, which could contribute to a comprehensive understanding of the imbibition behavior in realistic porous media.